However, it had both a subject and a timeframe that were peculiar. Googling the subject revealed news stories about it -- making it clear this was something the U.S. was interested in, but which would be no particular interest to anybody else.
The OP probably has a contractual duty to protect their client's identity & therefore can't take the risk that revealing more details would result in their client being identified.
That doesn't make sense.
The results of the query are probably private customer information, but the query itself has nothing to do with them (hopefully) and was simply the net the TLA was casting.
You've broken the seal by reporting that it was done at all and reporting the exact query doesn't change that.
OTOH, not reporting on what the actual query was makes me very skeptical about the whole thing.
By all means, obfuscate table names or whatever if there was a wildcard involve that matched customer defined elements (or whatever).